Substitute for natural feed ore



Patented Dec. 20, 1932 UNITED STATES PATENT; OFFICE JOHN M. HUGHES ANDJOSEPH H. CARTER, OF YOUNGSTOWN, OHIO, AND LEWIS IB.

PERKINS, 0F SHARON, PENNSYLVANIA,

ASSIGNORS TO SHARON STEEL HOOP COM- PANY, OF SHARON, PENNSYLVANIA, ACORPORATION OF PENNSYLVANIA SUBSTITUTE FOR NATURAL FEED ORE No Drawing.Application filed June 21,

During the working of the bath in the production of steel in open hearthfurnaces, electric furnaces or the like, it is usual to reduce thecarbon content by feeding thereinto at a suitable time before the heatis tapped, material adapted to act as a decarburizer, the quantity ofthe material utilized depending on the desired amount of carbonreduction, the individual characteristics of the particular bath beingworked, and other well known factors. The material ordinarily employedfor this purpose, and commercially known as feed ore, is a natural ironore containing a relatively high amount of one of the oxides of iron,generally in the form of Fe O or, less frequently, Fe O or FeO.

At the time this ore is introduced into the furnace, customarily bymerely manually throwing it through the charging doors, the metal of thebath is covered to a depth of several inches with a viscous anddifiicultly penetrable layer of slag, but in order to bring about theproper reactions and consequent decarburizing effect, it is necessaryfor the feed ore to penetrate this slag and enter the subjacent metal.When the pieces of ore are of sufiicient size and weight, this result isreadily accomplished but as the pieces become smaller and lighter theyincreasingly tend to float on or in the slag with correspondinglessening of the decarburizing effect which should theoretically beattained from a given amount of ore.

It is a well recognized fact in the steel industry that progressivelygreater difliculty is being experienced by consumers in obtaining feedore in pieces of sufficient size for satisfactory use, a ton of ore asnow furnished being ordinarily made up of some large sized pieces and anexcessive amount of relatively finely divided material of such characterthat it is substantially worthless for the purpose for which it waspurchased. \Vhether'this is due to increasing difficulty in mining therelatively few sources from which ore suitable for feeding purposes canbe obtained or to other causes not under the control of the 1930. SerialNo. 462,926.

burizing the bath in an open hearth furnace, at present only acomparatively small part thereof can be similarly employed, with theresult that the cost of production of the steel is materially increased.

Because of these and other conditions the provision of a substitute fornatural feed ore has become of distinct importance in the steel industrybut as far as we are aware no commencially satisfactory one has beenevolved prior to the present invention.

A principal object of our invention, therefore, is to provide asatisfactory substitute for the natural feed ore heretofore customarilyemployed for decarburizing the bath in the operation of open hearthfurnaces and which may be used similarly and in place of the natural orewith entirely satisfactory and, generally, improved results.

A further object of the invention is the provision of a substitute forthe natural ore which is capable-of giving a very quick reaction withthe bath and which may be prepared in pieces or masses of any size,shape and weight adapted to'rapidly penetrate the slag and alsoconvenient for use and of such form as to enhance the speed of thereaction in the furnace by afiording a maximum surface for contact withthe bath.

A still further object of the invention is to provide a substitute forthe natural ore which may be formed from readily obtainable materials,one of which may desirably be a by-product of certain of the operationsincident to the manufacture of steel and thus readily available in moststeel plants; which, in its preferred embodiment, may be lifted with amagnet for handling and transporta-.

ties and more iron than the average of the natural feed ores obtainable,while the fact that all of the pieces or masses may desirably be formedof the same size, shape and weight facilitates determination of theproper amount of the material to be used to effect a given extent ofdecarburization. Moreover,

the material can be manufactured at a cost be apparent to those skilled.in the art from' the following description of one manner of performingit.

In accordance therewith we prepare an aggregate of suitable iron bearingmaterial, which may be in the form of roll or hammer scale, iron ore, orthe like, roll scale being preferred, or a mixture of any or all of saidmaterials in any desired proportions, and a binder such as calciumaluminate and calcium silicate cement, Portland cement being ordinarilypreferred, although among other suitable binders any natural, slag orhydraulic cement can be utilized or a mixture of any or all of thesecements, the proportion of binder to the iron bearing material beingpreferably from two to twenty-five per cent. by weight, although undercertain conditions these limits may sometimes be exceeded. To thismixture we add sufficient water or other liquid to form a mass which maybe poured, pressed, rolled or otherwise conveniently formed into shapesor masses which on standing a sufficient length of time will harden orset at least enough to permit convenient handling or transportation. Wethen mold or otherwise form this plastic or semi-fluid material into thedesired shapes or masses which, after being allowed to harden for asuitable length of time, are then ready for employment as a substitutefor naturalore in feeding the furnace bath. In order to insure rapidpenetration of the slag covering thereof, the shapes or masses intowhich the plastic or semi-fluid mixture is molded or otherwise formed,and which for convenience we denominate blocks, are desirably made ofsufficient weight and size to readily effect this result, while,additionally, to facilitate the reaction in the furnace they are alsopreferably so shaped as to afford a large surface area for contact withthe bath. These conditions are well fulfilled when the material ismolded intocubes measuring approximately one foot on each side, butother shapes of different weights and sizesand either hollow or solid,may be utilized if preferred, it being ordinarily preferable to make theblocks as heavy as can be conveniently handled and thrown into thefurnace and with as large a surface area as possible commensurate withsuitable adaptability to penetrate the slag.

WVe have stated that we prefer to utilize roll scale as the iron bearingmaterial and have found that under most conditions the greater theamount of subdivision ofthe scale, the greater must be the amount ofcement combined therewith in order to produce a block or mass of thedesired hardness. Therefore, when using very finely divided scale, wepre er to mix the more finely divided scale with the less finely dividedas in that way we are enabled to obtain the desired degree of hardnessin the block with a proportionately smaller amount of cement. Thus wehave found that scale obtained from ordinary blooming mills may beutilized with relatively small amounts of cement, but that obtained fromlighter rolling mills requires relatively larger proportions thereofwhen used alone; it may, however, be mixed in reasonable quantities withthe less finely divided scale without necessiating the use of materiallygreater quantities of cement than would be required if the latter wereused alone.

Thus, by way of example, we may prepare a mixture of blooming mill scalein its natural condition, that is, just as it is produced during therolling operation, and Portland cement in the following proportions: 93%of scale and 7% of cement, by weight. To this we add enough water toenable the mass to be conveniently poured into molds adapted to formcubes measuring approximately 12" on each side, some tamping or otherpressure being preferably employed to assist in consolidatng thematerial in the molds. The mixture is then allowed to set until it issufficiently hard to permit removal from themolds without deformationand the molded blocks are then allowed to stand for a further length oftime until they attain a degree of hardness adequate to enable them tobe transported and handled without breakage. They are then in conditionto be fed to the furnae bath either immediately or at any subsequenttime, and are of sufficient weight (approximately 220 lbs. the specificgravity of the material being from 3.50 to 3.60) to readily penetratethe slag when they are thrown into the furnace.

Actual analysis of a block formed in this manner showed approximatelythe following: iron 67.05; phosphorus'.021; silica 2.1 1;

manganese .42; alumina .71; lime 4.03;

magnesia .27; sulphur .l-l, while a corresponding analysis on a drybasis of an average of five of the best known commercial natural feedores showed approximately: iron 59.66; phosphorus .348; silica 7.13;manganese .81; alumina 1.82; lime 2.31; magnesia .90; sulphur loss onignition 2.63.

It will thus be noted that our substitute for the natural feed ore issomewhat higher in iron oxide than the natural ore; it also containssome 1% to 2% of metallic iron which was not figured in the, foregoinganalysis and which enters the bath and adds to the metal thereof, sothat the increased efiiciency of the substitute based on iron alone isin the neighborhood of 8.3% while the smaller amount of impuritiescontained therein over the natural ore tends to the production ofcleaner steel. Moreover, because of the ability of the large andrelatively heavy blocks of the substitute material to penetrate and sinkbelow the slag, a greater decarburizing? effect is obtained than withthe natural ore even under the best conditions and with less loss irslag, while the uniformity in the size and weight of the blocks assistsmaterially in determining the proper quantity requisite to attain adesired degree of carbon reduction.

An additional advantage incident to the use of roll scale, or other ironbearing material having its iron oxide in the form of Fe o as thepredominant ingredient, resides in the fact that the blocks under theseconditions are magnetic and can thus be lifted and transported with amagnet, with consequent increase in the convenience and frequentlydecrease in the cost of handling.

While for the foregoing reasons, among others, we prefer under ordinaryconditions to employ roll scale or other like material as an ingredientof our substitute for natural feed ore, we may utilize the natural oreitself if preferred and either cintered or in its nat ural state, andthis will frequently be found advantageous when the natural ore can onlybe obtained in such finely divided condition as to make it more or lessunsuitable for feeding purposes. Moreover, through our invention, afield of use is created for large quantities of finely divided naturalore necessarily produced as an incident to the mining operations, forsuch ore may profitably be used as the iron bearing ingredient in theproduction of our substitute for natural feed ore. Of course, as theiron in most natural ores suitable for feeding purposes is in the formof F8203, the blocks of which it is the predominant ingredient arenon-magnetic and thus incapable of eing lifted with a magnet, anadvantage possessed by those in which the predominant iron bearingmaterial, such as roll scale, is magnetic as has been pointed out.

Practical use of our substitute for feed ore has demonstrated its entireadaptability for its intended purpose; has materially facilitated theoperation of decarburizing the bath and has shown that by its employmentin place of the natural feed ore a more rapid reaction may be obtained,the quality of the steel improved, and the other advantages attained towhich we hereinbefore referred.

Although we have herein described with considerable particularity, andby way of example only, one manner of performing our invention, we donot thereby desire or intend to in any way restrict or confine ourselvesthereto, nor to the use of any specific proportions of the iron bearingand/or cement or other binding material employed as the same are capableof a wide range of variation, while, additionally, any suitable manneror means for forming the plastic or semi-liquid mixture into blocks orother shapes may be utilized as preferred, without departing from thespirit and scope of the invention as defined in the appended claims.

Having thus described our invention, we claim and desire to protect byLetters Patent of the United States:

1. A substitute for natural feed ore consisting of a block formed fromover 93% by weight of F e 0 and the balance a binderconsistinosubstantially of Portland cement.

2. A su stitute for natural feed ore consisting of a block formed fromover 93% by weight of roll scale and the balance a binder consistingsubstantially of calcium-aluminosilicate cement.

3. A substitute for natural feed ore consisting of a block formed fromover 93% by weight of Fe3O and the balance a binder consistingsubstantially of calcium-alumino-silicate cement.

4. A substitute for natural feed ore consisting of a block formed fromover 93% by weight of roll scale and the balance a binder consistingsubstantially of Portland cement.

5. A decarburizing medium for molten steel consisting of a blockincluding an aggregate of from to 98% of iron oxide and the balance abinder composed substantiall of calcium-alumino-silicate cement.

In witness whereof, we have hereunto set our hands this 19th day ofJune, 1930.

JOHN M. HUGHES. JOSEPH H. CARTER. LEWIS B. PERKINS.

